The Californium-252 plasma desorption mass spectrometer puts unusual and stringent demands on the data system that controls the spectrometer and acquires and processes its data output. Real-time performance and the ability to access very large data arrays in main memory are key considerations. A data system design specification that meets these requirements has been drawn up and an evaluation of available hardware and software is under way. In addition, special interface electronics that will be required are also in the initial stages of design.